<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var num = prompt("请输入一个数字?");
        var reg = /^([0-9]|[1-9][0-9]|[1-5]\d{2}|6[0-5]\d|66[0-6])$/ ;
        if ( reg.test(num) ){
            alert(num+"满足在0-666");
        } else {
            alert(num+"不满足");
        }
    </script>
</body>
</html>